The CMMG 55D590A is a 16.1" stainless steel barrel assembly built for AR-15 platform rifles chambered in .223 Remington / 5.56 NATO. If you're assembling a custom upper receiver or replacing a worn barrel, this pre-assembled unit handles the critical work for you: the M4 extension is already installed and headspaced to spec, so you can focus on the build instead of troubleshooting fitment issues. The 416 stainless steel construction and bead-blasted finish resist corrosion and look professional while holding up to hard use in the field or at the range.

The medium taper profile keeps weight reasonable without sacrificing rigidity, and the 1:7 twist rate stabilizes a wide range of bullet weights from lightweight 55-grain rounds through heavier match ammunition. The 5.56 NATO chamber handles both military surplus and commercial loads. The midlength gas port and .750" gas journal pair with standard midlength tuning for a balanced cycling experience—not too soft, not overgassed.

Threading is 1/2-28, the industry standard for 5.56 muzzle devices, so you can thread on a suppressor, muzzle brake, or flash hider to suit your setup. Whether you're building a reliable duty rifle, a versatile hunting AR, or a precision range gun, a quality barrel assembly like this one is the foundation of accuracy and reliability.

The CMMG 55D590A is a 16.1" stainless steel barrel assembly built for AR-15 platform rifles chambered in .223 Remington / 5.56 NATO. If you're assembling a custom upper receiver or replacing a worn barrel, this pre-assembled unit handles the critical work for you: the M4 extension is already installed and headspaced to spec, so you can focus on the build instead of troubleshooting fitment issues. The 416 stainless steel construction and bead-blasted finish resist corrosion and look professional while holding up to hard use in the field or at the range.

The medium taper profile keeps weight reasonable without sacrificing rigidity, and the 1:7 twist rate stabilizes a wide range of bullet weights from lightweight 55-grain rounds through heavier match ammunition. The 5.56 NATO chamber handles both military surplus and commercial loads. The midlength gas port and .750" gas journal pair with standard midlength tuning for a balanced cycling experience—not too soft, not overgassed.

Threading is 1/2-28, the industry standard for 5.56 muzzle devices, so you can thread on a suppressor, muzzle brake, or flash hider to suit your setup. Whether you're building a reliable duty rifle, a versatile hunting AR, or a precision range gun, a quality barrel assembly like this one is the foundation of accuracy and reliability.